Page 1453 - Clinical Small Animal Internal Medicine

157 Approach to the Patient with Dermatologic Disease 1391

Table 157.3 (Continued)
VetBooks.ir Region Common diseases Less common diseases

Claws Hyperthyroidism, feline Bullous pemphigoid
Paronychia secondary to: Leishmaniasis
bacteria,fungi Onychomycosis
feline leukemia virus Pemphigus vulgaris
trauma Systemic lupus erythematosus
Pemphigus foliaceus Vasculitis
Physical trauma Vitiligo
Symmetric lupoid onychitis

sampling the center of the lesion, a more diagnostic allowed to completely air‐dry or is blow‐dried. A strip of
sample can be obtained by lifting the scales and crusts immersion oil is placed on the slide and the tape is
from the perimeter and sampling the edge of the lesion placed sticky side down on the strip of oil. Another drop
as described for crusts. of immersion oil is placed on top of the tape and micro-
Once the lesion is prepared for an impression, a glass scopic evaluation is performed at ×10 and ×100 magni-
slide should be gently pressed against the site, heat fixed fication. A cover slip is not needed.
(either by using a lighter passed under the slide until a
light smoky black residue is observed or by using a slide Surface Skin Scrape
warmer for 20 seconds) or allowed to air‐dry, and stained This technique is very useful when evaluating the skin
with a modified Wright’s stain (e.g., Diff‐Quik). Gram for bacteria and yeast and for sampling areas where an
stain or new methylene blue can also be used. When impression smear may be difficult to obtain. However, it
using Diff‐Quik (which the author prefers), allow the is best reserved for sampling affected areas that are
slide to sit in each reagent for approximately 20 seconds. greasy, otherwise the sample will not adhere well to the
Rinse the slide gently with water after the third solution. scalpel blade. A No. 10 scalpel blade is used to gently
The slide should then be air‐ or blow‐dried. scrape just the surface of the affected area in the direc-
The sample should first be evaluated under the micro- tion of the hair growth. It is not necessary to obtain cap-
scope using low‐power magnification (×10) to peruse for illary bleeding. Mineral oil is not utilized. The collected
an infectious versus inflammatory versus neoplastic pro- material is smeared onto a glass slide and heat fixed,
cess. The author finds it easiest to look for acantholytic stained, and microscopically evaluated according to the
cells and certain fungal organisms, such as blastomycosis, guidelines indicated above for impression smears.
under the low‐power objective, whereas immediate use of
the oil immersion objective (×100) may result in the miss- Cotton‐Tipped Applicator Smears
ing of rare organisms or cells. The oil immersion objective Cotton‐tipped applicators or swabs are useful for sam-
is then used (after a drop or two of immersion oil is placed pling moist lesions and intertriginous areas. The swab is
on the slide) to look for organisms and for closer observa- gently rubbed on the surface of the skin and the sample
tion and confirmation of inflammatory , neoplastic , and/ is then rolled onto a glass slide. This technique can also
or acantholytic cells. Draining nodules can also be evalu- be utilized for hard‐to‐reach areas where the skin is dry,
ated by directly pressing the slide to the draining contents except that the cotton swab is moistened with saline
and staining as previously described. prior to sampling in order to minimize cell damage dur-
ing sample collection and preparation. Once the sample
Acetate Tape Preparation is applied to the slide, it is heat fixed, stained, and evalu-
This technique is helpful for sampling intertriginous ated as described above for impression smears.
areas, nailfolds, interdigital areas, and dry, scaly, hyper-
plastic or lichenified skin surfaces. This is the author’s Otic Cytology Otic cytology is also performed using
preferred technique when Malassezia overcolonization cotton‐tipped applicators. Samples are obtained from
or infection is suspected. This test is performed by each external ear canal using a separate cotton swab.
pressing an approximately 2 cm piece of clear tape sticky A standard system should be used for making slides
side down firmly against the skin several times. The tape (i.e., the left ear sample is prepped next to the frosted
is then held at either end and immersed in the No. 3 side of the glass slide and the right ear sample on
Diff‐Quik stain for 15–20 seconds and then gently the other half of the slide). The slide is heat fixed and
rinsed with water to remove excess stain. The tape is stained as described above for impression smears. Begin